Scaling Examples; Scaled-For-Pid To Engineering Units; Engineering Units To Scaled-For-Pid; Proportional Counts To Engineering Units - Allen-Bradley SLC 500 1746-NR4 User Manual

Chapter 5
Channel Configuration, Data, and Status
The following examples are using the default scaling ranges:
Scaled–for–PID to Engineering Units
Equation: Engr Units Equivalent = S
Solution: Engr Units Equivalent = –200 C + [ (850 C – (–200 C) ) x (3421 / 16383) ] = 19.25 C.
Engineering Units to Scaled–for–PID
Equation: Scaled–for–PID Equivalent = 16383 x [ (Engineering Units desired – S
Solution: Scaled–for–PID Equivalent = 16383 x [ (344 C – (–200 C) ) / ( 850 C – (–200 C ) ) ] = 8488.

Proportional Counts to Engineering Units

Equation: Engr Units Equivalent = S
Solution: Engr Units Equivalent = 0W + { [1000W – (0W) ] x [ ( 21567 + 32768) / 65536 ] } = 829W.

Engineering Units to Proportional Counts

Equation: Proportional Counts Equivalent = { 65536 x [ ( Engineering Units desired – S
Proportional Counts Equivalent = { 65536 x [ (1809Ω – (0W) ) / (3000W– (0 W ) ) ] } – 32768 = 6750.
Solution:
5–8

Scaling Examples

+ [ (S – S
LOW HIGH LOW
Assume that the input type is an RTD, Platinum (
C) , scaled–for–PID display type. Channel data = 3421.
Want to calculate C equivalent..
From Channel Data Word Format ( Table 5.C through Table 5.H), S
C.
Assume that the input type is an RTD, Platinum (
C), scaled–for–PID display type. Desired channel temp. = 344 C.
Want to calculate Scaled–for–PID equivalent.
From Channel Data Word Format ( Table 5.C through Table 5.H), S
C.
+ { (S – S
LOW HIGH LOW
Assume that input type is a potentiometer (1000W, range = 0 to 1000W), proportional counts display
type. Channel data = 21567.
Want to calculate ohms equivalent.
From Channel Data Word Format ( Table 5.C through Table 5.H), S
Assume that input type is a potentiometer (3000W, range = 0 to 3000W), proportional counts display
type. Desired channel resistance value = 1809Ω . Want to calculate Proportional Counts equivalent.
From Channel Data Word Format (Table 5.C through Table 5.H), S
AB Spares
) x (Scaled–for–PID value displayed / 16383) ]
a =
,
200W
) / ( S
LOW
a =
,
200W
) x [ ( Proportional Counts value displayed + 32768) / 65536 ] }
LOW
, =
0.00385 C range –200 C to +850
= –200 C and S
LOW HIGH
– S ) ]
HIGH LOW
, =
0.00385 C range –200 C to +850
= –200 C and S
LOW HIGH
= 0W and S = 1000W.
LOW HIGH
) / ( S – S ) ] } – 32768
HIGH LOW
= 0W and S = 3000W.
LOW HIGH
= 850
= 850